Best way to build credit and recover after paying off debt?

Hi All!

In the final year of my studies I had to take out a loan to finish and graduate. Wasn't the best choice but it is what it is now I guess. It's haunted me for the last 4 years, and today I was FINALLY able to pay it all off!!!! (applause appreciated)

That said, I am looking for easy ways to start building my credit and improving my credit score. I wasn't able to be consistent with repayments until the last year which is the bad part. I am currently on 611 which is definitely not great. I am still young, finally earn good money and want to reign it in now while I've got the chance and no big commitments. I don't come from a wealthy family and thus was never taught financial literacy or anything like that, grew up paycheck to paycheck.

Any suggestions? Not sure who will let me open an account or give me any credit at this point which is sad but I won't make the same mistake again. Hoping I'm not out of options because I currently feel like I've ruined my life a little bit and not sure how to recover from this.

Edit: any advice on what I need to do to get credit bureaus to amend my credit record (now that I've paid debt off) would also be appreciated! As you can see I am very unsure of where to go from here.